In recent years, hybrid vehicles that use an engine and a motor in combination have rapidly become widely used to achieve higher fuel efficiency. On the other hand, marketing of electric vehicles that can run by a motor alone is in progress. To be feasible, these vehicles require use of a power converter for AC/DC conversion between a battery and the motor.
In the hybrid and electric vehicles, the semiconductor power converter is expected to be small and highly reliable. To this end, the power converter requires high cooling efficiency. As a measure to achieve this, a power converter structure of the double-sided cooling type has been proposed in which electrical conductors are connected individually to the obverse and reverse surfaces of a semiconductor element and heat is released from the electrical conductors to a cooler.
A plurality of semiconductor devices (semiconductor modules) must be arranged in the semiconductor power converter. In the case where electricity is used to drive the axle of an automobile, high voltage and high current are applied such that the semiconductor devices produce much heat, thus requiring consideration of electrical insulation between terminals. It is difficult, therefore, to increase the packaging density of the semiconductor devices.